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THE CHANGING ATMOSPHERE-CHALLENGES AND OPPORTUNITIES

[[image - color photo of view of the Antarctic]]
[[caption]] Human-induced increases in some trace gases have been implicated in the sudden and large springtime decrease of ozone over the Antarctic. (Photo by Charles Smythe.) [[/caption]]

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thermal expansion of water. By the next century, we will see an acceleration of these trends, as other trace gases contribute as much as carbon dioxide, and thus more than double the overall greenhouse effect.

The human-induced increases in some of the trace gases, such as chlorofluorocarbons (CFCs), have been implicated in the sudden and large springtime decrease of ozone over the Antarctic, and in a lesser but significant decrease in ozone over the rest of the world during the entire year. The most familiar hazard associated with decreasing ozone is an expected increase in skin cancer. But a potentially far greater threat to life is the destruction and mutation of simple forms of marine and terrestrial life, upon which the food chain depends. Recognizing the global threat, more than 30 nations have taken preliminary steps, through the Montreal Protocol, to cut back on the emissions of certain chlorofluorocarbons. Even so, experts predict that the concentrations of these trace gases will continue to increase well into the next century. We need to understand the climatic variations that may be triggered by these changes in order to plan intelligently.

Human activities are also changing characteristics of the earth's surface, such as reflectivity and moisture availability. Tropical deforestation is one major impact, but changes are occurring in middle latitudes as well as a result of increasing urbanization and agricultural activities.

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